1. Field of the Invention
This invention relates to a mask, and more particularly, to a mask, a method of fabricating the same, and a method of fabricating organic electro-luminescence device using the same that is capable of minimizing a difference of a rigidity coefficient value of both an open part and an blocking part.
2. Description of the Related Art
Recently, there have been developed various flat panel display devices reduced in weight and bulk that is capable of eliminating disadvantages of a cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence (EL) display, etc. device.
In such flat panel display devices, the PDP has the most advantage for making a large dimension screen because its structure and manufacturing process are simple, but has a drawback in that it has low light-emission efficiency and large power consumption. The LCD has a difficulty in making a large dimension screen because it is fabricated by a semiconductor process, but has an expanded demand as it is mainly used for a display device of a notebook personal computer. However, the LCD has a drawback in that it has a difficulty in making a large dimension screen and it has large power consumption due to a backlight unit. Also, the LCD has characteristics of a large light loss and a narrow viewing angle due to optical devices such as a polarizing filter, a prism sheet, a diffuser and the like.
On the other hand, the EL display device is largely classified into an inorganic EL device and an organic EL device. When compared with the above-mentioned display devices, the EL display device has advantages of a fast response speed, large light-emission efficiency, a large brightness and a large viewing angle. The organic EL display device can display a picture at approximately 10[V] and a high brightness of ten thousands of [cd/m2].
FIG. 1 is a plan view illustrating a related art organic electro-luminescence (EL) display device, and FIG. 2 is a sectional view illustrating the organic EL display device taken along a line II-II′ in FIG. 1.
Referring to FIGS. 1 and 2, the related art organic EL display device comprises a insulating film 6, a barrier rib 8, and an organic layer 10, formed between an anode electrode 4 and a cathode electrode 12. The anode electrode 4 and the cathode electrode 12 are crossing so as to insulate from each other.
A plurality of anode electrodes 4 is provided on the substrate 2 in such a manner to be spaced at a predetermined distance from each other. A first driving signal is supplied to such the anode electrode 4 in order to emit an electron (or hole).
The insulating film 6 is formed in a lattice type so as to expose an aperture for each EL cell area on the substrate 2 having the anode electrode 4.
The barrier rib 8 is formed in a direction crossing the anode electrode 4, and is formed in parallel to the cathode electrode 12 by a predetermined distance to partition adjacent EL cells. In other words, the barrier rib 8 separates the organic layers 10 from each other and the cathode electrodes 12 from each other between the adjacent EL cells. Further, the barrier rib 8 has an overhang structure in which the upper portion thereof has a larger width than the lower portion thereof.
The organic layer 10 is made from an organic compound on the insulating film 6. In other words, the organic layer 10 is formed by depositing a hole carrier layer, a light-emitting layer and an electron carrier layer onto the insulating film 6.
A plurality of cathode electrodes 12 is provided on the organic layer 10 in such a manner to be spaced at a predetermined distance from each other, and in such a manner to be crossed with the anode electrodes 4. A second driving signal is supplied to the cathode electrode 12 in order to emit an electron (hole).
The substrate 2 having the cathode electrode 12 is protected by use of a packaging plate 14. In other words, the packaging plate 14 covers the anode electrode 4, the cathode electrode 12, and the organic layer 10 formed on the substrate 2, by using an sealant (not shown), so as to prevent the organic layer 10 from being deteriorated by moisture and oxygen in the atmosphere. After pressuring the packaging plate 14 to the substrate 12 to encapsulate the anode electrode 4, the cathode electrode 12, and the organic layer 10, the sealant is hardened by irradiating an ultraviolet ray. After encapsulating, an inert gas is injected in a space formed by sealing the substrate 2 and the packaging plate 14. At this time, the encapsulated atmosphere is performed in a globe box or a vacuum chamber.
In the organic EL device, when the first and the second driving signals are respectively applied to the anode electrode 4 and the cathode electrode 12, an electron and a hole are emitted. The electron and the hole emitted from the anode electrode 4 and the cathode electrode 12 recombine in the organic layer 10, and at the same time, visible rays are generated. At this time, the generated visible rays are emitted to the exterior via the anode electrode 4, to thereby display a predetermined picture or image.
Meanwhile, the related art organic layer 10 is formed by using a shadow mask 60 having an open part 60a and a blocking part 60b, as shown in FIG. 3.
In a case that the shadow mask 60 is applied to an organic EL device of a high resolution having a relatively small pixel, as a size of the pixel becomes smaller, a width of the open part 60a becomes narrower and a thickness of the shadow mask becomes thinner so as to prevent a damage of the barrier rib greatly contacting with the shadow mask. For instance, when a size of the pixel is 100 μm, a thickness of the shadow mask 60 is approximately 50 μm. The shadow mask 60 having a relatively thin thickness has a difficult problem to secure a plan property as compared with the shadow mask having a relatively thick thickness. To solve this problem, by stretching the shadow mask 60, a tension force of a predetermined magnitude is applied to the shadow mask 60, to thereby prevent a modification of the shadow mask 60. However, because the open part 60a of the shadow mask 60 has a small rigidity coefficient value as compared with the blocking part 60b, the open part 60a and the open part 60b are stretched unequally. An accuracy of alignment of both the unequally stretched shadow mask 60 and the substrate becomes lower. Accordingly, when the organic layer 10 is formed by use of the unequally stretched shadow mask 60, an organic layer of a different color is formed at an area of an organic layer having a special color or an organic layer is not formed at an area of the organic layer. Thus, there is a problem that a yield becomes lowered.